The urines of 7,944 students (aged 5--25 years) from 42 different localities in Northern KwaZulu were screened for the presence of Schistosoma haematobium eggs. Fifty-four percent were infected, but prevalence varied from 8--92% depending on conditions existing in the localities. The age-specific prevalence in each of the four topographical areas was unusual in that peaks were not distinct and sharp decreases towards the end of the 2nd decade of life did not occur. Egg output, determined by using a helminth filter and staining of eggs, was expressed in relation to time (2-hour mid-day specimens) rather than urine volume. Unlike the prevalence, egg output decreased considerably after a distinct peak which occurred at 8 years of age in the low prevalence area and at ages 10 and 11 years in the heavily infected areas. Statistical analyses of the results revealed that the observed prevalence of S. haematobium was dependent on area and age but not on sex. The significance of the findings in this area are discussed.